Mesh sheet for curved surface formation and storage bag formed by mesh sheet

ABSTRACT

The present invention provides a mesh sheet and a container bag which, when formed into a three-dimensional shape with a curved surface, have the ability to retain and recover said shape, and which are less prone to wrinkling, and the like. Warp threads 1a and weft threads 1b are formed by arranging first fibers 2 which comprise a single component and second fibers 3 which have at least a double-layer structure of a core portion and a sheath portion covering the surface of the core portion and in which the melting point of the component forming the sheath portion is at least 20° C. lower than whichever is lower from among the melting point of the component forming the core portion and the melting point of the first fibers 2. At least the second fibers 3 are provided to both the warp threads 1a and the weft threads 1b, and the interlacing sections of the second fibers 3 constituting the warp threads 1a and the second fibers 3 constituting the weft threads 1b are thermally bonded. The percentage of thermally bonded interlacing sections of second fibers 3, 3 among all of the interlacing sections of the warp threads 1a and the weft threads 1b is 10% to 45%.

TECHNICAL FIELD

The present invention relates to a mesh sheet for curved surface formation and a storage bag formed using the mesh sheet.

BACKGROUND ART

A tea bag formed into a polyhedron, such as a tetrahedron, by folding and fusion-bonding a planar sheet made of non-woven fabric or mesh fabric is widely used as a disposable tea bag for extracting components of tea or the like into liquid (see, for example, Patent Literature 1 below).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent No. 3956019

SUMMARY OF INVENTION Technical Problem

A tea bag in the shape of a triangular pyramid or a cube disclosed in Patent Literature 1 has a shape hard to maintain and is easily deformable, and shape resiliency after deformation is small. Thus, the tea bag has a problem. The problem is that a filter has difficulty in spreading in liquid at the time of component extraction to hinder tea leaves from spreading or moving. A conventional mesh fabric used in such a tea bag, in particular, is hard to be provided with shape retentivity and resiliency after deformation when the mesh fabric is formed into a three-dimensional body. Since the mesh fabric decreases in flexibility if the mesh fabric is provided with shape retentivity or the like, the mesh fabric is likely to wrinkle when the mesh fabric is formed into a curved surface shape, such as a spherical shape.

Under the circumstances, the present inventions provide a mesh fabric which has shape retentivity and resiliency and is resistant to wrinkling when the mesh fabric is formed into a three-dimensional shape having a curved surface, and a beverage extraction bag formed of the mesh fabric.

Solution to Problem

In a mesh sheet for curved surface formation according to the present invention, a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and a fusion-bonding rate for the interlaced portions of the second fibers in all of interlaced portions in the warp and the weft is not less than 10% and not more than 45%.

With the above-described configuration, the mesh sheet according to the present invention has spherical shape retentivity and resiliency and is resistant to wrinkling when the mesh sheet is formed into a three-dimensional shape having a curved surface.

In a mesh sheet according to the present invention, a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and the number of the second fibers constituting the warp and the weft to a sum of the numbers of the first fibers and the second fibers is not less than 33% and not more than 70%.

With the above-described configuration, the mesh sheet according to the present invention has spherical shape retentivity and resiliency and is resistant to wrinkling when the mesh sheet is formed into a three-dimensional shape having a curved surface.

One or two of the first fibers and one or two of the second fibers may be alternately arranged in the warp forming the mesh sheet according to the present invention, and one or two of the first fibers and one or two of the second fibers may be alternately arranged in the weft.

A same number of the first fibers and the same number of the second fibers may be alternately arranged in either one of the warp and the weft forming the mesh sheet according to the present invention, the same number being one or two, and three of the first fibers and one of the second fibers may be alternately arranged in the other of the warp and the weft.

Either one of the warp and the weft forming the mesh sheet according to the present invention may be made only of ones of the second fibers, and three of the first fibers and one of the second fibers may be alternately arranged in the other of the warp and the weft.

Fiber densities of the warp and the weft forming the mesh sheet according to the present invention may be not less than 70 fibers and not more than 120 fibers per inch.

The first fibers and the second fibers forming the mesh sheet according to the present invention may be monofilaments.

With the above-described configuration, transparency, tension, and elasticity of the first fibers and the second fibers are easy to maintain.

A storage bag according to the present invention includes any one of the above-described mesh sheets, and the mesh sheet is formed in a three-dimensional shape having a curved surface.

With the above-described configuration, the storage bag has an action or a function of any one of the above-described mesh sheets.

Advantageous Effect of Invention

The mesh sheets and the storage bag according to the present invention have an advantageous effect in that each of the mesh sheets and the storage bag has shape retentivity and resiliency and is resistant to wrinkling when the mesh sheet or the storage bag is formed into a three-dimensional shape having a curved surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 1B is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 1C is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 1D is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 1E is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 1F is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 2A is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 2B is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 2C is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 3 is a plan view showing a part of a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 4A is a plan view showing a part of an example to be compared with a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 4B is a plan view showing a part of an example to be compared with a mesh sheet according to an embodiment of the present invention on an enlarged scale.

FIG. 5 is a view schematically showing a storage bag according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENT

Embodiments of a mesh sheet and a storage bag capable of retaining a curved surface according to the present invention will be described below with reference to the drawings.

As the mesh sheet according to the present invention, a mesh plain weave fabric in which at least one(s) of interlaced portions is (are) thermally fusion-bonded by heat treatment (also referred to as “setting”) is used.

As filaments forming the mesh sheet, a first fiber which is made of a single component and a second fiber which uses a plurality of components different in melting point from the first fiber are used.

A synthetic fiber which is made of polyethylene, polypropylene, polyurethane, nylon, polyester, polylactic acid, or the like and has thermal adhesiveness is used as the first fiber. In particular, polyester, polylactic acid, nylon, or the like is more preferably used.

Also, either a monofilament or a multifilament can be used as the first fiber. A monofilament, in particular, is more preferably used in the mesh sheet according to the present invention in terms of retaining fiber transparency, tension, and elasticity.

In the present embodiment, a monofilament made of a homopolyester is used an example of the first fiber. Note that a homopolyester in the present specification refers to a polycondensate of ethylene glycol and terephthalic acid which are polyester fiber components currently in widespread use.

A fiber which has a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion to form a fiber surface is used as the second fiber. In the present embodiment, a fiber which has a two-layer structure with a core and a sheath is used as the second fiber.

The same component as the first fiber can be used as a component for forming the core portion.

A component lower by 20° C. or more than a lower one of the melting point of the first fiber and a melting point of the component for the core portion is used as a component for forming the sheath portion.

Like the material for the first fiber, a synthetic fiber which is made of polyethylene, polypropylene, polyurethane, nylon, polyester, polylactic acid, or the like and has thermal adhesiveness can be used as a material for the core portion of the second fiber. In particular, polyester, polylactic acid, nylon, or the like is preferably used for a material for the core portion of the second fiber. A material with a melting point lowered in the manner described earlier by adding a different component to the material for the core portion or adjusting the degree of polymerization, or the like can be used as a material for the sheath portion of the second fiber.

Either a monofilament or a multifilament can be used as the second fiber. A monofilament, in particular, is more preferably used in the mesh sheet according to the present invention in terms of retaining fiber transparency, tension, and elasticity.

In the present embodiment, a monofilament using polyester for the core component and a polyester fiber containing terephthalic acid and isophthalic acid for the sheath component is used as an example of the second fiber. Note that the polyester fiber containing terephthalic acid and isophthalic acid refers to a fiber which is made of a polymer in which ethylene terephthalate as well as ethylene isophthalate is included in a polyester molecule.

The ratio of the core component in the second fiber is preferably not less than 50 vol % and not more than 75 vol %. If the ratio of the core component to the whole second fiber is less than 50 vol %, the ratio of the sheath component to the whole is not less than 50 vol %, and the mesh sheet cannot withstand temperatures for fabric scouring and finishing processes. The degree to which an interlaced portion of second fibers is fusion-bonded increases, the firm nature of the whole of each fiber is lost, and the fiber becomes significantly soft. That is, shape retainability of a storage bag becomes insufficient. On the other hand, if the ratio of the core component is not less than 75 vol %, the second fiber becomes too firm, a storage bag becomes firm to the touch to easily cause wrinkles, and bending recoverability decreases.

Thicknesses of the first fiber and the second fiber may be not less than 15 dtex and not more than 60 dtex. The thicknesses of the first fiber and the second fiber are preferably 20 to 35 dtex, more preferably 22 to 33 dtex. In the case of a fineness of 20 to 35 dtex, weaving stability in a weaving process at the time of weaving is excellent, and a woven mesh sheet good in texture (flexibility) is easily obtainable.

The mesh sheet is a sheet obtained by plain-weaving a warp in which first fibers and second fibers are regularly arranged and a weft in which first fibers and second fibers are regularly arranged and thermally fusion-bonding each interlaced portion of second fibers in the warp and the weft such that the second fibers do not peel off from each other.

Heat treatment for the mesh sheet is set at a temperature lower than a lower one of the melting point of a first fiber and the melting point of a core portion of a second fiber and higher than the melting point of a sheath portion. The heat treatment is performed by a method generally used by those skilled in the art.

A fiber density of the mesh sheet can be set to 70 or more to 120 or less fibers per inch by 70 or more to 120 or less fibers per inch.

With heat treatment of the mesh sheet, each interlaced portion of second fibers is thermally fusion-bonded to the extent that the fibers do not slide past each other. Since only a sheath portion of a second fiber melts at an interlaced portion of a first fiber and the second fiber, the interlaced portion is not completely fusion-bonded, and the first fiber and the second fiber are in a state in which the first and second fibers are fusion-bonded with a strength lower than the extent that the first and second fibers can peel off from each other or are not fusion-bonded. An interlaced portion of first fibers is in a state in which the first fibers are not fusion-bonded to each other.

The “extent that fibers slide past each other” here means that a part of a fusion-bonded interlaced portion is peeling off or peels off without a fiber fracture to cause slippage of space between threads.

An interlaced portion fusion-bonding rate of the mesh sheet, i.e., the ratio of interlaced portions of second fibers fusion-bonded to each other to interlaced portions over the whole mesh sheet is set to fall within a range of not less than 10% to not more than 45% of the whole.

In other words, the number of second fibers constituting the warp and the weft to the sum of the numbers of first fibers and second fibers constituting the warp and the weft of the mesh sheet is set to fall within a range of not less than 33% to not more than 70%.

Various examples are conceivable as an arrangement pattern for first fibers and second fibers in the warp and the weft which satisfies the above-described interlaced portion fusion-bonding rate or the above-described ratio of the total number of second fibers to the sum of the numbers of first fibers and second fibers used in the warp and the weft constituting the mesh sheet. As for the mesh sheet, for which various arrangement patterns are available, an overlap (hereinafter referred to as an “arrangement pattern smallest region” S) between a smallest unit for an arrangement pattern of first fibers and second fibers constituting the warp and a smallest unit for an arrangement pattern of first fibers and second fibers constituting the weft is set to calculate the interlaced portion fusion-bonding rate. The interlaced portion fusion-bonding rate can be calculated by dividing the “total number of interlaced portions of second fibers” in the arrangement pattern smallest region S by the “total number of interlaced portions over the whole”. The ratio of second fibers in the whole sheet can be calculated by dividing the “total number of second fibers” in the arrangement pattern smallest region S by the “sum of the numbers of first fibers and second fibers”.

The reason why the interlaced portion fusion-bonding rate of the mesh sheet is set not less than 10% of all interlaced portions is as follows. If the fusion-bonding rate is less than 10% (i.e., the total number of second fibers to the sum of the numbers of first fibers and second fibers constituting the mesh sheet is less than 33%), the mesh sheet tries to return to a flat shape at the time of forming the mesh sheet into a three-dimensional body having a curved surface, such as a spherical shape, which makes a curved surface hard to form (makes the mesh sheet likely to become flat).

The reason why the interlaced portion fusion-bonding rate of the mesh sheet is not more than 45% of all the interlaced portions is as follows. If the fusion-bonding rate is more than 45 (i.e., the total number of second fibers to the sum of the numbers of first fibers and second fibers constituting the mesh sheet is more than 70%), the mesh sheet is hardened and has insufficient bounce at the time of forming the mesh sheet into a three-dimensional curved surface, especially a spherical shape or the like, and resiliency (or a return force) after the curved surface is deformed is insufficient. Another reason is that the mesh sheet is likely to wrinkle at the time of being formed into a curved surface due to insufficient flexibility.

Note that the interlaced portion fusion-bonding rate of the mesh sheet is preferably not less than 12% and not more than 40%, most preferably 25%. The ratio of second fibers in the whole mesh sheet is more preferably not less than 30% and not more than 65%, most preferably 50%.

Examples of a mesh sheet having an arrangement pattern of first fibers and second fibers in a warp and a weft, in which an interlaced portion fusion-bonding rate is not less than 10% and not more than 45% or the ratio of second fibers in the whole sheet is not less than 33% and not more than 70%, include the ones below.

[1] A mesh sheet in which a warp having one or two first fibers and one or two second fibers alternately arranged and a weft having one or two first fibers and one or two second fibers alternately arranged are plain-woven and in which the second fibers are fusion-bonded

Specific examples of the arrangement pattern include the patterns below.

(i) A pattern in which the same numbers (one or two) of first fibers (2) and second fibers (3) are alternately arranged both in a warp (1 a) and a weft (1 b) of the mesh sheet (1), as illustrated in FIG. 1A or 1B (ii) A pattern in which one first fiber (2) and one second fiber (3) are alternately arranged in the warp (1 a) of the mesh sheet (1) and two first fibers (2) and two second fibers (3) are alternately arranged in the weft (1 b), as illustrated in FIG. 1C (iii) A pattern in which one first fiber (2), one second fiber (3), one first fiber (2), and two second fibers (3) are arranged in this order in the warp (1 a) of the mesh sheet (1) and the same numbers (one or two) of first fibers (2) and second fibers (3) are alternately arranged in the weft (1 b), as illustrated in FIG. 1D or 1E. (iv) A pattern in which one first fiber (2), one second fiber (3), one first fiber (2), and two second fibers (3) are arranged in this order both in the warp (1 a) and the weft (1 b) of the mesh sheet (1), as illustrated in FIG. 1F. (v) A pattern not illustrated in which a pattern for the warp (1 a) of each of the mesh sheets (1) in (ii) to (iv) and a pattern for the weft (1 b) are interchanged. [2] A pattern in which the same number (one or two) of first fibers (2) and second fibers (3) are alternately arranged in either one (the weft (1 b) in this example) of the warp (1 a) and the weft (1 b) of the mesh sheet (1) and three first fibers (2) and one second fiber (3) are alternately arranged in the other (the warp (1 a) in this example) of the warp (1 a) and the weft (1 b), as illustrated in FIG. 2A or 2B [3] A pattern in which only second fibers (3) are used in either one (the weft (1 b) in this example) of the warp (1 a) and the weft (1 b) of the mesh sheet (1) and three first fibers (2) and one second fiber (3) are alternately arranged in the other (the warp (1 a) in this example) of the warp (1 a) and the weft (1 b), as illustrated in FIG. 3

Arrangement patterns which satisfy conditions on the interlaced portion fusion-bonding rate and the proportion of the second fibers (3) in the whole mesh sheet (1) are not limited to the above-described ones. According to the conditions, for example, an arrangement pattern in which there are three or more crossings of the first fibers (2) in a row both in a lengthwise direction and a crosswise direction is excluded.

EXAMPLES

Examples of the present invention will be illustrated below. Note that the present invention is not limited to the contents illustrated in the examples.

Example 1

A fiber (22 dtex) made of a homopolyester component was used as a first fiber (2), and a polyester fiber (28 dtex) having a core-in-sheath structure, in which a core portion was made of the same component as the first fiber (2), a sheath portion was made of a polyester having a melting point of 190° C., and the ratio of the core portion in the whole second fiber (3) was 50 vol %, was used as the second fiber (3).

As illustrated in FIG. 1A, a plain-woven mesh sheet (1) in which one first fiber (2) and one second fiber (3) were alternately arranged both in a warp (1 a) and a weft (1 b) was used. The mesh sheet (1) was refined, was water-washed and dried, and then was subjected to heat treatment at 195° C.

After that, a forming heater temperature was set to 140° C., and the mesh sheet (1) after the heat treatment was put in a die and was formed into a hemispherical shape.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of the second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of a hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Example 2

As illustrated in FIG. 1B, heat treatment was performed using a mesh sheet (1) which was formed in the same manner as in Example 1 except that two first fibers (2) and two second fibers (3) were alternately arranged both in a warp (1 a) and a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Example 3

As illustrated in FIG. 1C, heat treatment was performed using a mesh sheet (1) which was formed in the same manner as in Example 1 except that one first fiber (2) and one second fiber (3) were alternately arranged in a warp (1 a) and that two first fibers (2) and two second fibers (3) were alternately arranged in a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Example 4

As illustrated in FIG. 2A, heat treatment was performed using a mesh sheet (1) which was formed in the same manner as in Example 1 except that three first fibers (2) and one second fiber (3) were alternately arranged in a warp (1 a) and that one first fiber (2) and one second fiber (3) were alternately arranged in a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Example 5

As illustrated in FIG. 2C, heat treatment was performed using a mesh sheet (1) which was formed in the same manner as in Example 1 except that two first fibers (2) and two second fibers (3) were alternately arranged in a warp (1 a) and that three first fibers (2) and one second fiber (3) were alternately arranged in a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Example 6

As illustrated in FIG. 3, heat treatment was performed using a mesh sheet (1) which was formed in the same manner as in Example 1 except that three first fibers (2) and one second fiber (3) were alternately arranged in a warp (1 a) and that only second fibers (3) were used in a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (1), the ratio of second fibers (3) in the whole mesh sheet (1), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Comparative Example 1

As illustrated in FIG. 4A, heat treatment was performed using a mesh sheet (X) which was formed in the same manner as in Example 1 except that three first fibers (2) and one second fiber (3) were alternately arranged both in a warp (1 a) and a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (X), the ratio of second fibers (3) in the whole mesh sheet (X), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Comparative Example 2

As illustrated in FIG. 4B, heat treatment was performed using a mesh sheet (X) which was formed in the same manner as in Example 1 except that one first fiber (2) and one second fiber (3) were alternately arranged in a warp (1 a) and that only second fibers (3) were used in a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (X), the ratio of second fibers (3) in the whole mesh sheet (X), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

Comparative Example 3

Heat treatment was performed using a mesh sheet (X) which was formed in the same manner as in Example 1 except that only second fibers (3) were used both in a warp (1 a) and a weft (1 b) under the same conditions as in Example 1, and a hemisphere was formed.

A result of determining an interlaced portion fusion-bonding rate of the formed mesh sheet (X), the ratio of second fibers (3) in the whole mesh sheet (X), a projection height, a shape, and resilience of the hemisphere, and the presence/absence of wrinkles near an opening portion is shown in Table 1.

TABLE 1 An Interlaced Portion Fusion- The Ratio bonding Of Second The Rate Of Fibers A Projection Presence/Absence The Formed In The Height Of A Shape Resilience Of Wrinkles Near Mesh Sheet Whole Mesh The Hemisphere Of The Of The An Opening (%) Sheet (mm) Hemisphere Hemisphere Portion Example 1 25 50 16.3 close to a Good Few perfect Example 2 25 50 16.2 close to a Good Very Few perfect Example 3 25 50 16.2 close to a Good Few perfect Example 4 12.5 33.3 16.1 close to a Good Very Few perfect Example 5 12.5 37.5 16.1 close to a Good Almost None perfect Example 6 25 62.5 16.2 close to a Good Few perfect Comparative 6.3 25 15.2 flat Good Very Few Example 1 Comparative 50 75 16.7 close to a Average Many Example 2 perfect Comparative 100 100 17.8 close to a Poor Very Many Example 3 perfect

[Evaluation Method]

A fusion-bonding rate for interlaced portions of second fibers (3) with respect to all interlaced portions and the ratio of second fibers (3) to all first and second fibers (2) and (3) used in each mesh sheet (1) were calculated by the calculation methods described earlier. Note that although Example 6 and Comparative Example 2 each use only second fibers (3) in the weft (1 b), the number of fibers in a smallest unit for an arrangement pattern for the weft (1 b) was set equal to the number of fibers in a smallest unit for an arrangement pattern for the warp (1 a) to view a ratio in the whole.

As for a shape of a formed sphere, whether an outer edge of a curve was close to a perfect circle or seemed flat was judged by visual inspection. As for resilience, whether a formed hemisphere returned to an original shape when the hemisphere was slowly pressed with a finger to the extent that the hemisphere was dented was judged by visual inspection. Resilience was evaluated on a scale of Good (returned), Average (remained slightly dented), and Poor (remained dented). Wrinkles near an opening portion were evaluated by visual inspection on a scale of almost none (indiscernible), very few, few, many, and very many.

[Evaluation Result]

As indicated by Table 1, in each of the formed hemispherical bodies according to Examples 1 to 6, a shape of the sphere was kept having a beautiful shape close to a perfect circle, and the resilience was sufficient. There were almost no, very few, or few wrinkles near the opening portion, and the wrinkles were not noticeable.

In a case where a storage bag (10) was formed by butt-joining opening portions of formed bodies according to each of Examples 1 to 6 and heat-sealing the opening portions along a whole circumference with tea leaves inside, as illustrated in FIG. 5, the storage bag (10) maintained a generally beautiful spherical shape and had sufficient resilience, and wrinkles at the opening portions were hardly noticeable.

In Comparative Example 1, since three interlaced portions of the first fibers (2) in a row were regularly arranged both in a lengthwise direction and a crosswise direction, and the fusion-bonding rate was low, shape retainability was low. The extent of return to a mesh sheet shape after the formation into a spherical shape was large, and the hemisphere took a somewhat flat shape. In each of Comparative Examples 2 and 3, the fusion-bonding rate was too high, the resilience was low, and the spherical body had difficulty recovering its shape when the spherical body was dented.

As described above, the mesh sheet (1) according to the present invention has advantageous effects in that a desired curved shape is easily obtainable when the mesh sheet (1) is formed into a three-dimensional shape having a curved surface, such as a sphere, and that the mesh sheet (1) can be provided with shape retainability and resilience (deformation resiliency). The mesh sheet (1) according to the present invention also has an advantageous effect in that, when the storage bag (10) in a spherical shape or the like (e.g., a beverage extraction bag in a spherical shape or the like) is formed using the mesh sheet (1), the storage bag (10) having shape retainability and resiliency after deformation can be formed.

Note that use of the mesh sheet (1) according to the present invention has an advantageous effect in that a tea bag in a somewhat flat spherical shape, an elliptical shape, or the like which has a shape restoring force after deformation can be satisfactorily formed, in addition to a storage bag in a generally spherical shape.

REFERENCE SIGNS LIST

-   1: mesh sheet -   1 a: warp -   1 b: weft -   2: first fiber -   3: second fiber -   10: storage bag 

1. A mesh sheet for curved surface formation, wherein a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and a fusion-bonding rate for the interlaced portions of the second fibers in all of interlaced portions in the warp and the weft is not less than 10% and not more than 45%.
 2. A mesh sheet for curved surface formation, wherein a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and the number of the second fibers constituting the warp and the weft to a sum of the numbers of the first fibers and the second fibers is not less than 33% and not more than 70%.
 3. The mesh sheet for curved surface formation according to claim 1, wherein one or two of the first fibers and one or two of the second fibers are alternately arranged in the warp, and one or two of the first fibers and one or two of the second fibers are alternately arranged in the weft.
 4. The mesh sheet for curved surface formation according to claim 1, wherein a same number of the first fibers and the same number of the second fibers are alternately arranged in either one of the warp and the weft, the same number being one or two, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 5. The mesh sheet for curved surface formation according to claim 1, wherein either one of the warp and the weft is made only of ones of the second fibers, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 6. The mesh sheet for curved surface formation according to claim 1, wherein fiber densities of the warp and the weft are not less than 70 fibers and not more than 120 fibers per inch.
 7. The mesh sheet for curved surface formation according to claim 1, wherein the first fibers and the second fibers are monofilaments.
 8. (canceled)
 9. The mesh sheet for curved surface formation according to claim 2, wherein one or two of the first fibers and one or two of the second fibers are alternately arranged in the warp, and one or two of the first fibers and one or two of the second fibers are alternately arranged in the weft.
 10. The mesh sheet for curved surface formation according to claim 2, wherein a same number of the first fibers and the same number of the second fibers are alternately arranged in either one of the warp and the weft, the same number being one or two, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 11. The mesh sheet for curved surface formation according to claim 2, wherein either one of the warp and the weft is made only of ones of the second fibers, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 12. The mesh sheet for curved surface formation according to claim 2, wherein fiber densities of the warp and the weft are not less than 70 fibers and not more than 120 fibers per inch.
 13. The mesh sheet for curved surface formation according to claim 2, wherein the first fibers and the second fibers are monofilaments.
 14. A storage bag comprising a mesh sheet for curved surface formation, wherein a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and a fusion-bonding rate for the interlaced portions of the second fibers in all of interlaced portions in the warp and the weft is not less than 10% and not more than 45%, wherein the mesh sheet is formed in a three-dimensional shape having a curved surface.
 15. The storage bag according to claim 14, wherein one or two of the first fibers and one or two of the second fibers are alternately arranged in the warp, and one or two of the first fibers and one or two of the second fibers are alternately arranged in the weft.
 16. The storage bag according to claim 14, wherein a same number of the first fibers and the same number of the second fibers are alternately arranged in either one of the warp and the weft, the same number being one or two, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 17. The storage bag according to claim 14, wherein either one of the warp and the weft is made only of ones of the second fibers, and three of the first fibers and one of the second fibers are alternately arranged in the other of the warp and the weft.
 18. The storage bag according to claim 14, wherein fiber densities of the warp and the weft are not less than 70 fibers and not more than 120 fibers per inch.
 19. The storage bag according to claim 14, wherein the first fibers and the second fibers are monofilaments.
 20. A storage bag comprising a mesh sheet for curved surface formation, wherein a warp and a weft are formed by arranging first fibers which are made of a single component and second fibers which each have a structure with at least two layers of a core portion and a sheath portion covering a surface of the core portion, a melting point of a component for forming the sheath portion being lower by 20° C. or more than a lower one of a melting point of a component for forming the core portion and a melting point of the first fibers, both the warp and the weft include at least ones of the second fibers, and interlaced portions of the second fibers constituting the warp and the second fibers constituting the weft are thermally fusion-bonded, and the number of the second fibers constituting the warp and the weft to a sum of the numbers of the first fibers and the second fibers is not less than 33% and not more than 70%, wherein the mesh sheet is formed in a three-dimensional shape having a curved surface.
 21. The storage bag according to claim 20, wherein one or two of the first fibers and one or two of the second fibers are alternately arranged in the warp, and one or two of the first fibers and one or two of the second fibers are alternately arranged in the weft. 